vasp测试计算机,科学网—PWSCF 自洽计算、kpoints测试和ecut测试

关注：

1) 自洽计算的目的是为了check结构建立是否合理，程序能否顺利运行；

2) kpoints测试的重要性；选择合适的参数，可在保证质量的情况下，节省计算时间

3) ecut 测试的重要行

经验总结：

1) 赝势选取后，测试赝势的截断能，最初值设置参考依据是…..？从赝势文件中能看出来吗？

保模势范围60 ~120 Ry；超软势范围30~40Ry；VASP里面的一般都很小

2) 测试判据：前后两点之间能量差会越来越小吗？感觉实际不会…..采用脚步文件进行截断能测试也需要建立一系列的临时文件夹吗？

一般截断能越大越好；差值会越来越小，但实际情况可能由于收敛的问题会出现一个虚假的小值后，接着出现一个正常的偏差值，并在随后随着截断能的增加，该差值变小。一般90Ry够了

3) no hup.out 文件中，经常碰到：

application called MPI_Abort(MPI_COMM_WORLD, 0) - process 0

并行问题

(3)关于赝势在处理计算体系中原子的电子态时，有两种方法，一种是考虑所有电子，叫做全电子法，比如WIEN2K中的FLAPW方法(线性缀加平面波)；此外还有一种方法是只考虑价电子，而把芯电子和原子核构成离子实放在一起考虑，即赝势法。

一般赝势法是选取一个截断半径，截断半径以内，波函数变化较平滑，和真实的不同，截断半径以外则和真实情况相同，而且赝势法得到的能量本征值和全电子法应该相同。赝势包括模守恒和超软，模守恒较硬，一般需要较大的截断能，超软势则可以用较小的截断能即可。另外，模守恒势的散射特性和全电子相同，因此一般红外，拉曼等光谱的计算需要用模守恒势。

ecutwfcREAL

Status:REQUIRED

kinetic energy cutoff (Ry) for wavefunctionsecutrhoREAL

Default:4 * ecutwfc

kinetic energy cutoff (Ry) for charge density and potential

For norm-conserving pseudopotential you should stick to the

default value, you can reduce it by a little but it will

introduce noise especially on forces and stress.

If there are ultrasoft PP, a larger value than the default is

often desirable (ecutrho = 8 to 12 times ecutwfc, typically).

PAW datasets can often be used at 4*ecutwfc, but it depends

on the shape of augmentation charge: testing is mandatory.

The use of gradient-corrected functional, especially in cells

with vacuum, or for pseudopotential without non-linear core

correction, usually requires an higher values of ecutrho

to be accurately converged.ecutwfcREAL

Status:REQUIRED

kinetic energy cutoff (Ry) for wavefunctionsecutrhoREAL

Default:4 * ecutwfc

kinetic energy cutoff (Ry) for charge density and potential

For norm-conserving pseudopotential you should stick to the

default value, you can reduce it by a little but it will

introduce noise especially on forces and stress.

If there are ultrasoft PP, a larger value than the default is

often desirable (ecutrho = 8 to 12 times ecutwfc, typically).

PAW datasets can often be used at 4*ecutwfc, but it depends

on the shape of augmentation charge: testing is mandatory.

The use of gradient-corrected functional, especially in cells

with vacuum, or for pseudopotential without non-linear core

correction, usually requires an higher values of ecutrho

to be accurately converged.

并行问题

网言摘录：

1)根据所要求的精度不同，收敛标准也是不一样的。通常，总能变化在10来个meV，这样精度就比较高了。(2)最好是你提到的那样，弄个总能～ecut的图。(3)在测试ecut时，k点网格也不能太小(你提到的2x2x2对大多数情况是不合理的)。同理在测试k-mesh时，ecut的值也不能太小(你提到的2Ha也是在大多数情况下是不合理的)，这些特别是在原胞小的体系，而且体系曾金属性或带隙很小时，k-mesh和ecut测试时都不能取的太小。也要有适当的精度。

Q::::你的原胞中有5个原子吧，而且看你的光学支振动频率，金属原子应该原子质量比较大吧，应该有很强的局域性，所以，可以试一下超软赝势，而且模守恒赝势取45Ry确实很小啊，呵呵。

Q：：：

"We are going to use ultrasoft pseudopotentials here. In the case of norm-conserving pseudopotentials from Lab 2, ecutrho (the charge density cutoff) is automatically determined by 4*ecutwfc. However, in the case of ultrasoft pseudopotentials, we need an augmented charge around the ion core, so ecutrho should be higher than 4*ecutwfc. The usual value is 25-35 Ry for ecutwfc and 200-300 Ry for ecutrho. You might want to do a convergence check. Keep in mind that the value you should look at is the energy difference or force, not the absolute value of the energy (the energy will not converge unless you use very, very high ecutwfc and ecutrho). "

对于所有的第一性原理的计算，你必须注意两个收敛问题，第一是能量截断，也就是波函数展开的截断。第二是k 点的个数，它意味着离散格子对连续积分的近似度。

在实际的计算中，我们必须限制平面波在某些点扩展(就是停止取得更多的G)，这叫做平面波的截断。截断总是取能量单位(如Rydberg 或eV)，对应于最高的动能。

为了得到晶体的能量值, 我们必须在整个第一Brillouin区积分, 在第一Brillouin 区,能带被占据(并被体积划分)。因此，对有限的k 点求和的到积分的近似值，你必须保证有足够的k 点得到收敛的能量值。

ecutrho：kineticenergy cutoff (Ry) for charge density and potential

May be larger ( for ultrasoftPP ) or somewhat smaller

( but not much smaller )than the default value. Note that

if you have norm-conservingPP only, setting it to a larger

value than the default is awaste of time.

1. run_scf

###########self-consistent calculation ######################

for ecut in 80

cat > $name.scf.in_$ecut << EOF

&control

calculation = 'scf'

restart_mode='from_scratch',

prefix='$name',

pseudo_dir = '$PSEUDO_DIR/',

outdir='$TMP_DIR/'

tstress=.t.,

tprnfor=.t.

&system

ibrav=0,

nat=10,

ntyp=2,

ecutwfc= $ecut, ecutrho = 760.0

occupations ='smearing', smearing ='mp',degauss =0.02

&electrons

mixing_beta = 0.7

conv_thr = 1.0d-7

ATOMIC_SPECIES

H 1.008 H.pbe-van_ak.UPF

Sc 44.9559 Sc.pbe-nsp-van.UPF

CELL_PARAMETERS {bohr}

4.745568648 -4.27115E-08 0

-4.27115E-08 4.745568539 -9.49146E-09

4.74573E-09 -1.89829E-08 8.842464528

ATOMIC_POSITIONS {crystal}

H 0.499999965 0.500000040 0.370850743

H 0.499999950 0.500000054 0.629149579

H -0.000000022 0.000000030 0.870851011

H -0.000000027 0.000000036 0.129148779

H -0.000000013 0.500000019 0.249999381

H -0.000000012 0.500000019 0.750000700

H 0.499999968 0.000000027 0.249999365

H 0.499999976 0.000000024 0.750000717

Sc -0.000000006 -0.000000010 0.499999832

Sc 0.500000021 0.500000003 0.000000162

K_POINTS {automatic}

4 4 4 0 0 0

EOF

$MPIDIR/mpirun -np $NP -machinefile $CURDIR/.nodelist $EXEDIR/pw.x < $name.scf.in_$ecut >$name.scf.out_$ecut

done

2. kpoints测试

####################kpoints test#############################

kmeshs="10,10,6 \

12,12,7 \

14,14,8 \

16,16,9 \

20,20,11"

for a in $kmeshs

cat > $name.scf.in_$a << EOF